Various respiratory protection devices are used to supply clean air to their users. In some cases, clean air is made available to the user by first drawing ambient air through a filter that is disposed in a filter cartridge. The filter cartridge can be attached to a respirator mask body that is worn on a person's face, over his or her nose and mouth. In such respiratory protection devices, ambient air is drawn through the filter due to negative pressure created by the wearer's inhalation. In other methods, clean air may be supplied to the user under pressure from a blower that forces ambient air through a filter. Such pressurized devices are known as powered air purifying respirators or PAPRs. Alternatively, clean air can be furnished to a user of a respiratory protection device from a pressurized tank. Such a device is known as a self-contained breathing apparatus or SCBA. In each of these devices, a clean air supply source (such as a filter cartridge or a hose from a PAPR or SCBA) is connected to a mask body that is worn over the nose and mouth of the user. The eyes and head may be covered as well if the user desires full face and head protection.
Several types of systems have been developed in the respirator art for attaching the clean air source to the respiratory mask. One common system uses a threaded component that is attached to a corresponding threaded fitting—see, for example, U.S. Pat. Nos. 5,222,488, 5,063,926, 5,036,844, 5,022,901, 4,548,626, 4,422,861 and 6,575,165. The threaded filter cartridges typically possess helical or advancing spiral threads that mate with a tapped collar or socket. Rotating the filter cartridge in an appropriate direction allows the cartridge to be attached to or removed from the respirator body. A resilient, deformable gasket has been used to ensure that an airtight fit is maintained at the interface. Detents have been used to releasably lock a threaded clean air supply in place. See, e.g., U.S. Pat. No. 6,575,165.
In lieu of a threaded attachment mechanism, bayonet type closures have been used to attach clean air sources to respirators. The bayonet type closure has locking tabs and notches to secure the components together. The locking tabs may project from a filter cartridge and may engage the notches in an aperture on the respirator body. When the filter cartridge is rotated in the appropriate direction, the cartridge engages the mask body—see U.S. Pat. Nos. 6,216,693 and 5,924,420. The benefit of using a bayonet-type fitting is that the cartridge can engage the mask body with a quick turn, usually less than about one-half turn.
An audible indication device has been used in bayonet closure systems to indicate that the filter cartridge is properly coupled to the respirator face piece—see U.S. Pat. Nos. 4,934,361, and 4,850,346. A lug on the face piece has been provided with a détente ramp or cam that has an inclined surface, which is positioned to gradually deflect or deform a rib on the cartridge. As the cartridge and face piece are rotated relative to each other into a locking position, the cam engages the rib and causes the rib and lug to deflect until the rib abruptly drops off the end of the cam. The abrupt action produces the audible click.
Respirators that have snap-fit filter cartridges also have been designed as shown in U.S. Pat. No. 5,579,761 to Yushack et al. In this approach, the filter cartridge is instantaneously snapped into engagement with the mask body simply by pressing the cartridge against a corresponding receiving structure on the mask body. No rotational movement of the filter cartridge is needed.
Also known are respiratory protection devices, in which threaded portions of the clean air supply source and the clean air receiving structure engage each other at a high thread pitch and include an integral détente. A stop prevents over-rotation of the clean air supply source relative to the mask body during the securement operation. See U.S. Pat. No. 7,320,722 to Mittelstadt et al.